Although not specifically shown, a this type of a conventional air damper includes a tubular cylinder which are opened at both end portions, a piston which moves within the cylinder, and a cap which closes a one-end opening of the cylinder. In the cylinder, an annular seal surface is formed on an inner circumferential surface side of the one-end opening, and the cap has a disk-like base plate which is mounted in the one-end opening of the cylinder so as to move along an axial direction of the cylinder and an annular seal flange which extends from the base plate so as to project in a radial direction, one orifice being opened in the base plate (for example, refer to Patent Document 1).
Consequently, in the case of this air damper being used in an glove box of an automotive vehicle, the cylinder is fixed rotatably to an instrument panel side, and a distal end portion of a piston rod which projects from the other-end end portion of the cylinder is fixed rotatably to the glove box side. Then, when the glove box is moved towards an opening direction, the piston rod is gradually pulled out of an interior of the cylinder, and the piston moves in the same direction within the cylinder. However, at this point in time, since the base plate of the cap is allowed to move by a change in pressure within the cylinder, whereby the seal flange of the cap comes into close contact with the seal surface of the cylinder in a perfect fashion, it is ensured that the glove box moves slowly to an open state by a flow resistance of air which passes through the one orifice.
In contrast, when the glove box is moved towards a closing direction, since the piston rod is gradually pushed into the cylinder in response to the movement of the glove box, the piston also moves in the same direction within the cylinder. However, at this time, the base plate of the cap moves in a reverse direction through the air within the cylinder by a change in pressure within the cylinder, so as to cause the seal flange to move away from the seal surface of the cylinder to thereby cause the air within the cylinder to escape to the outside. By this, a closing operation of the glove-box is promoted.
Patent Document 1: JP-2000-065116-A